1. Field of the Invention
The present invention relates to monorail transportation systems in general and, more specifically, to monorail transportation systems wherein a vehicle may be attached to the monorail for travel therealong or separated from the monorail for independent travel.
2. Description of Prior Art
Monorail transportation systems, and other overhead rail transportation systems, have been proposed as a means for reducing traffic congestion. In a monorail system, a vehicle is typically suspended beneath an overhead rail such that the vehicle is elevated above the ground. By elevating the rail above the ground, the land surface under the rail may be used for standard roadways to increase the volume of traffic that a given area may service, or to permit the land to be used for other purposes. Alternatively, a multiple rail overhead system has been used wherein a vehicle is suspended from, travels along, or travels between multiple rails.
Monorail transportation systems lend themselves well to mass transit wherein a discrete number of vehicles each capable of holding a large number of people are used, much like subway systems. However, due to the reluctance of the public to use mass transit and the necessity of stations for the loading and unloading of passengers, it has been found beneficial to adapt small occupancy vehicles for travel along the monorail.
One proposal to adapt a small occupancy vehicle for travel along a monorail uses a specially designed vehicle that is capable solely of traveling along the monorail system. Although this permits small numbers of individuals to freely travel along a monorail system, such a system is inconvenient because users must still travel from their homes to a separate location for boarding a vehicle on the monorail system.
Other proposals for adapting vehicles for travel along monorail systems permit the vehicles to travel on ordinary road surfaces when separated from the monorail system. However, these attempts suffer from other drawbacks. Specifically, one attempt modifies a bus-like vehicle for suspension underneath a monorail. In this device, the bus may travel independently from the monorail along ordinary road surfaces. To travel along the monorail, the bus is attached to a motor unit that is a permanent component of the monorail. Although such a system permits a vehicle to travel independently of the monorail, it requires that the system include a large number of motor units permanently attached to the monorail. Thus, to provide continuous service along the monorail, motor units must be spaced along the entire system. This increases the cost and complexity of the overall system and also increases the cost of operation as all the drive units must be continuously driven along the monorail.
A similar proposal adapts ordinary automobiles for travel along a monorail by securing a suspending tube on the top of the automobile. The suspending tube suspends the automobile from a motorized trolley car that is permanently attached to the monorail. While this system permits the automobile to be driven independently from the monorail system, it too requires a continuous supply of trolley cars along the monorail system. Further, the suspending tube presents an unsightly appearance when the automobile is traveling independently from the monorail.
One proposal to eliminate the need for drive units permanently attached to the monorail system is to adapt a vehicle to travel between two vertically displaced rails. In this system, a vehicle includes a plurality of guide wheels on the roof of the vehicle that are spaced to grip the sides of the upper rail for providing lateral support to the vehicle while traveling along the system. The bottom of the vehicle includes side wheels for providing lateral support while traveling on ordinary road surfaces and a central drive wheel that propels the vehicle along the lower rail. Although such a system eliminates the need for drive units permanently attached to the monorail system, the guide wheels on the roof of the vehicle present an unsightly appearance. Additionally, a new vehicle substantially different from existing automobiles would be required for operation on the system. Still further, by suspending the vehicle between upper and lower rails, it would be difficult to remove a vehicle from the system should it become disabled.
An additional problem associated with all currently proposed systems is that the guide wheels are too small to withstand the high rotational speed needed for the vehicle to travel at high speeds. In particular, with small guide wheels, the bearings would tend to break down in operation and require frequent maintenance.